
In Balance of Power!, Ash used Grovyle as his third and final Pokémon in his Petalburg Gym Battle against Norman, going up against Norman's final Pokémon, his Slaking. With Exploud obeying Guy again, Ash decided to finish the battle using Grovyle again. Team Rocket then tried to capture Exploud again but Guy was able to protect it, earning its respect. Ash and the others eventually caught up with Grovyle and Exploud with Ash and Guy deciding to pick up the battle, with Exploud ignoring Guy's commands again. After Team Rocket angered Exploud, Grovyle heard Exploud and followed it to a waterfall, battling it again. While looking for Exploud, Grovyle refused to return to its Poké Ball and went to higher ground, which caused May to comment that Grovyle was more stubborn after evolving. Ash and Guy decided to continue the battle, but Exploud ignored its Trainer's commands, rampaging off.

Grovyle demonstrated its new Leaf Blade attack, putting a twig in its mouth. After battling hard both Pokémon evolved at the same time, Loudred into Exploud and Treecko into Grovyle. Ash decided to battle Guy and his Loudred as he thought exercise could solve its problems and Treecko volunteered itself to battle. Guy mentioned his Loudred had been acting weird lately, which Ash compared to his Treecko. The Loudred's rampage was stopped by its Trainer Guy. All of a sudden a Loudred started rampaging through the area, which caught Treecko's interest. This worried Max but Ash assumed that it was just in a bad mood. In Exploud and Clear!, while the other Pokémon ate food Treecko didn't eat and acted distant, hiding up a tree and ignoring attempts by Ash and Corphish to be friendly. Treecko battled Brawly's Hariyama again in Just One of the Geysers and won, earning Ash the Knuckle Badge. In Turning Over a Nuzleaf, when it and the other Pokémon were separated from their Trainers, Treecko frequently taunted Aron and Corphish, though they later made amends in order to beat Team Rocket. Brock pointed out that even though Grass-types are strong against Rock-types, Treecko did not have an advantage due to it not knowing any Grass-type moves. In The Winner by a Nosepass, Ash chose Treecko to battle Roxanne's Geodude, where it quickly lost. It then battled the Seviper again and won. Later in the episode, Treecko went off to do some special training on its own when it had perfected a new variation of Pound in which it spun in the air before hitting the target. In the next episode, Treecko struggled to make friends with the other Pokémon until it rescued May's Torchic from a wild Seviper, though it was badly hurt in the process.

Soon afterward, it had a battle with Ash's Pikachu and Ash caught it as a result.

Treecko was caught in Tree's a Crowd after Ash helped it in trying to save its old tree home.
